A pyroelectric infrared ray sensor using the pyroelectric effect, a variable resistance infrared ray sensor using the rate of change with temperature of the resistance of a material, a junction type infrared ray sensor using a change in electrical properties of a semiconductor p-n junction and the like are known as infrared ray sensors. The pyroelectric and variable resistance infrared ray sensors that can operate at room temperature are used for fire detection, human body detection and the like. In such an infrared ray sensor, a plurality of infrared ray detection elements are arranged in an array, so that a highly sensitive sensor can be obtained.
An infrared ray sensor that includes a linear array type pyroelectric element (10) in which a plurality of receiving surface electrodes (2a, 2b etc.) in a line pattern are formed on the front surface of a pyroelectric base (1), and a plurality of counter surface electrodes (4a, 4b etc.) in the same pattern are formed on the rear surface thereof and further includes thereon an infrared ray pass filter (50) that allows only infrared rays with a desired wavelength to pass and a lens dome (60) including a spherical Fresnel lens is illustrated in FIGS. 1 and 2 of Patent Literature 1 (FIG. 4). In this structure, infrared rays generated in a detection area are condensed by the Fresnel lens (60) and incident on the pyroelectric element (10), so that infrared rays over a wide range can be detected.
A linear array type infrared ray sensor in which a plurality of pyroelectric elements (11) in a line pattern having electrodes formed on both surfaces of pyroelectric ceramics are mounted on an element support (14) is illustrated in FIG. 1 of Patent Literature 2.
In order to detect infrared rays over a wide range without using a condenser lens such as a Fresnel lens in the pyroelectric infrared ray sensor, a pyroelectric base (2) that has been patterned into a shape capable of condensing light is proposed in FIG. 1 of Patent Literature 3, for example.
A CO2 concentration detector including a light emitting unit that emits infrared rays in a wavelength band for absorbing carbon dioxide and a pyroelectric infrared ray detection element that receives infrared rays through an optical filter that transmits only the infrared rays emitted from the light emitting unit is disclosed in Patent Literature 4 (claim 1). In this detector, the infrared ray sensor is irradiated with infrared rays for measurement of a specific wavelength band, and gas detection is conducted using the fact that an increase in the ambient CO2 concentration leads to a decrease in the quantity of infrared rays received by the infrared ray detection element (see the 17th 21st rows of the fourth column).